There is a need for the coating material for an electric wire and cable that is halogen-free, inexpensive, that have a low specific gravity, that is flame retardant, heat resistant, and flexible, and that support high productivities. Non-Patent Document 1 and Patent Document 1 proposes flame-retardant resin compositions comprising polyphenylene ether, which is rigid, low fluidity, high dimensional stability, and high flame retardancy; and a hydrogenated copolymer, which is high flexibility, and easily extrusion molded, containing an aromatic vinyl monomer unit and a conjugated diene monomer unit; and a phosphorus flame retardant.
Among the proposed flame-retardant resin compositions, reducing a content of the polyphenylene ether in the composition is one tactic for responding to the requirements for flexibility and productivity for coating materials. However, the flame retardancy is reduced if the content of polyphenylene ether is reduced. On the other hand, if a total content of the flame retardant is increased in order to improve the flame retardancy, the problem arises of bleed out of the flame retardant in the resin composition with elapsed time.
In addition, when an electric wire or cable comes into contact with the housing or casing, which is made of ABS resin or polycarbonate, for a household electrical appliance or consumer electronics device, the flame retardant and/or plasticizer migrate into the housing or casing. This causes a defective appearance.
Regarding such the flame-retardant resin, various compositions have been proposed.
Patent Document 1 proposes a flame retardant comprising a mixture of ammonium phosphate, a metal hydroxide, and a phosphate ester. However, as described in Non-Patent Document 2, ammonium phosphate generally has a low heat resistance and a high hygroscopicity. Moreover, phosphate esters are prone to bleed out to the surface of the composition.
Patent Document 2 proposes a flame-retardant resin composition comprising 15 parts by weight or more but less than 45 parts by weight of polyphenylene ether, from 0 to 30 parts by weight of a styrene polymer, from 10 to 60 parts by weight of a hydrogenated copolymer containing a copolymer block obtained by a hydrogenation of a copolymer comprising a conjugated diene monomer unit and an aromatic vinyl monomer unit, and from 3 to 40 parts by weight of a phosphorus-type flame retardant selected from phosphorus red, phosphate esters, phosphazene compounds, and phosphoramide compounds. However, the compositions proposed as examples exhibit a low flexibility, a distinct tendency for bleed out to occur, and a distinct tendency for component migration to occur upon contact with another resin such as ABS.
Patent Document 3 discloses a flame-retardant resin composition that contains a phosphorus-containing compound, aromatic resin, a nitrogen-containing compound, a metal salt of an inorganic acid, and a compound having a functional group that is reactive with the active hydrogen atom or a water-repellent compound. However, there is no mention of a hydrogenated copolymer principally comprising an aromatic vinyl monomer unit and a conjugated diene monomer unit. Therefore, the productivity and the flexibility are inadequate.    Non-Patent Document 1: Leading Edge Ecomaterials by Takashi YOSHIDA, Japan Electric Cable Technology Center, Inc., p. 31 (2004)    Non-Patent Document 2: Flame Retardant Technology of Polymeric Materials Hitoshi NISHIZAWA by Hitoshi NISHIZAWA, CMC Publishing Co., Ltd. (2002)    Patent Document 1: International Publication No. 2005/097900    Patent Document 2: Japanese Patent Application Laid-open No. 2006-225477    Patent Document 3: International Publication No. 2003/046084